1. Field of the Invention
The present invention relates to a device for adjusting the tilt angle of an optical pickup used for an optical recording and reproducing apparatus for effecting recording or reproduction with respect to a compact disk, an optical disk, or the like.
2. Description of the Related Art
An optical pick up has the function of applying laser light upon a disk, and unless the direction of application of the laser light is adjusted appropriately, optical aberrations occur, so that drawbacks such as a decline in a signal level occurs. For this reason, a tilt-angle adjusting step for appropriately adjusting the direction of application of the laser light with high accuracy is included in the process of fabrication of the optical pickup. A conventional tilt-angle adjusting device for effecting the tilt-angle adjusting step is shown in FIG. 13, and the configuration of a leaf spring used in the tilt-angle adjusting device is shown in FIG. 14. Further, the operation based on the tilt-angle adjusting device is shown in FIG. 15.
In FIG. 13, reference numeral 1 denotes an optical base serving as a main base. A spherical seat 3 is provided on a bottom plat 2 of this optical base 1. Reference numeral 4 denotes an actuator on which a lens unit (not shown) for application of laser light is mounted, and the actuator 4 has supported portions 5. The supported portions 5 are mounted and supported on the spherical seat 3 of the optical base 1 in such a manner as to be tiltable about a center X (see FIG. 15) of the spherical seat 3. For this reason, the actuator 4 is tiltable about the center X.
A leaf spring 6 is screwed down in a predetermined position on the optical base 1. One portion of a base 7 of the actuator 4 is resiliently pressed by this leaf spring 6 at an eccentric position from the spherical seat 3, and the supported portions 5 of the actuator 4 are pressed against the spherical seat 3 by its resiliently pressing force. Meanwhile, threaded holes 8 and 9 are provided at two other portions of the base 7 of the actuator 4, and screwed into these threaded holes 8 and 9 are tilt-angle adjusting screws 10 and 11 inserted from the reverse side of the bottom plate 2 into screw insertion holes (not shown) provided in the bottom plate 2 of the optical base 1. In this state, the tilt-angle adjusting screws 10 and 11 are rotatably fitted at fixed positions on the optical base 1. Here, the portion a of the base 7 which is resiliently pressed by the leaf spring 6 is located at an eccentric position from the spherical seat 3. Similarly, the threaded holes 8 and 9 into which the tilt-angle adjusting screws 10 and 11 are screwed are also located at eccentric positions from the spherical seat 3, and the resiliently pressed portion a and the two threaded holes 8 and 9 are arranged in such a manner as to be distributed on both sides with the center X of the spherical seat 3 placed therebetween.
As shown in FIG. 14, the leaf spring 6 is formed by a single flat plate material having an attaching portion 12 and a resilient piece portion 13. As shown in FIG. 13, the attaching portion 12 is fixed to the optical base 1 by means of a screw 14 and, as shown in FIG. 15, the resilient piece portion 13 is in resilient contact with a receiving piece portion 15 provided on the base 7 in a state of being superposed on the receiving piece portion 15. For this reason, the direction of the resiliently pressing force applied to the receiving piece portion 15 of the actuator 4 by the leaf spring 6 has been substantially vertical as shown by arrow F1 in FIG. 1, i.e., substantially parallel to the axis P of the tilt-angle adjusting screw 10.
On the other hand, JP-A-11-273104 and JP-A-63-129524 give descriptions of optical pickups. Of these publications, JP-A-63-129524 proposes an optical pickup in which the tilt angle of the optical pickup is adjusted by making use of screws and a coil spring. In this optical pickup as well, the resiliently pressing force of the coil spring is parallel to the axial direction of the screw.
However, with the conventional tilt-angle adjusting device described with reference to FIGS. 13 to 15, it was found that when the actuator 4 is tilted by rotating the two tilt-angle adjusting screws 10 and 11 to effect the adjustment of the tilt angle of the optical pickup, since its adjustable range is narrow and the torque required for the tilt-angle adjusting screws 10 and 11 changes substantially depending on the amount of rotation, if the amount of rotation becomes large, the required torque becomes excessively large, and the tilt-angle adjusting screws 10 and 11 become difficult to rotate, with the result that it is difficult to ensure adjustment accuracy. On the other hand, if the amount of rotation is small, the required torque becomes excessively small, with the result that the adjustment sensitivity declines. Furthermore, it was found that since the resiliently pressing force applied to the receiving piece portion 15 of the actuator 4 by the leaf spring 6 is constituted by only a substantially downwardly oriented force, and the situation is such that practically no horizontal component is generated, the actuator 4 is likely to produce a horizontal positional offset.
The invention has been devised in view of the above-described circumstances, and its object is to provide a device for adjusting the tilt angle of an optical pickup by using a leaf spring and tilt-angle adjusting screws, which makes it possible to expand the adjustable range of the tilt angle, in which the torque required for rotating the tilt-angle adjusting screw ceases to change so much depending on the amount of rotation so as to make it possible to effect the adjustment of the tilt angle smoothly with high sensitivity, and in which the actuator is difficult to cause a horizontal positional offset, by allowing the resiliently pressing force imparted to the actuator by the leaf spring to generate a vertical component and a horizontal component.
The device for adjusting the tilt angle of an optical pickup includes: an optical base having a spherical seat; an actuator having supported portions supported by the spherical seat in such a manner as to be tiltable about a center of the spherical seat; a leaf spring for pressing the supported portions against the spherical seat by resiliently pressing a portion of a base of the actuator at an eccentric position from the spherical seat; and a tilt-angle adjusting screw fitted rotatably to a fixed position on the optical base and screwed down in a threaded hole at another portion of the base at an eccentric position from the spherical seat. Further, the direction of a resiliently pressing force applied to the actuator by the leaf spring is tilted with respect to an axis of the tilt-angle adjusting screw.
According to the above-described arrangement, the resiliently pressing force imparted to the actuator by the leaf spring generates a vertical component and a horizontal component. Accordingly, the adjustable range of the tilt angle expands, and the torque required for rotating the tilt-angle adjusting screw ceases to change so much depending on the amount of rotation to make it possible to effect the adjustment of the tilt angle smoothly with high sensitivity. Furthermore, the actuator is difficult to cause a horizontal positional offset.
Preferably, the leaf spring includes an attaching piece portion which is attached to the optical base, a resilient piece portion continuing from the attaching piece portion, and an applying portion which is provided in the resilient piece portion and is in resilient contact with the one portion of the base. As a specific example of such a leaf spring, it is possible to suitably use one having the following structure.
Namely, it is possible to suitably use a leaf spring in which the resilient piece portion has a projection extending diagonally upward from the attaching piece portion and a turned-back piece portion extending diagonally downward from a projecting end of the projection on a lower side of the projection through a U-shaped turning back portion, the applying portion being provided on the turned-back piece portion. In this case, the base may be formed in the shape of a flat plate, and the turned-back piece portion of the leaf spring may be tilted with respect to a plate surface of the base.
Further, it is preferred that the attaching piece portion of the leaf spring be screwed down to the optical base, and that a sliding piece portion which is substantially parallel to the plate surface of the base be provided continuing from a lower end of the turned-back piece portion. If this leaf spring is used, when the applying portion of the turned-back piece portion is brought into resilient contact with one portion of the base of the actuator, the sliding piece portion slides on the plate surface of the base and the applying portion of the turned-back piece portion is guided to one portion of the base. Therefore, a situation is difficult to occur in which the leaf spring is fitted on the optical base in a state in which a distal end of the turned-back piece portion remains abutting against the base.
Further, it is preferred that a projecting piece portion which can be clamped by a jig when the attaching piece portion is screwed down to the optical base be provided uprightly on the attaching piece portion. If this leaf spring is used, since the projecting piece portion can be clamped by a tweezers-like jig, and the attaching piece portion can be screwed down to the optical base, the operational efficiency further improves at the time when the leaf spring is fitted on the optical base.
In the invention, it is preferred that two threaded holes be provided as the threaded hole at circumferential portions of an outer periphery of the spherical seat, and that the distance between one of the threaded holes and a resiliently pressed portion of the base which is resiliently pressed by the leaf spring and the distance between another one of the threaded holes and the resiliently pressed portion are set to be identical or substantially identical. By adopting this arrangement, it becomes possible to accurately effect the adjustment of the tilt angle in the radial direction and the tangential direction by the two tilt-angle adjusting screws.